Reducing scale in vinyl polymerizations

Abstract

Disclosed is a method of inhibiting the formation of scale on reactor surfaces in contact with a polymerizing vinyl monomer. The reactor surfaces are contacted with a composition that contains, as a scale reducing agent, an acidic hydrazone condensate or a salt thereof. The scale reducing agent can be added to the polymerizing monomer or it can be placed in a composition containing a surfactant and an inorganic binder and the composition can be applied to the reactor surfaces or added to the monomer.

We claim: 
     
       1. A method of inhibiting the formation of scale on reactor surfaces in contact with a polymerizing vinyl monomer comprising contacting said reactor surfaces with a scale reducing agent that comprises an acid hydrazone condensate or a salt thereof. 
     
     
       2. A method according to claim 1 wherein said acid hydrazone condensate has the general formula ##STR5## where each R is independently selected from the group consisting of hydrogen, alkyl from C 1  to C 15 , and aryl, alkaryl, aralkyl, alkarythio, and aralkylthio from C 6  to C 15 , X is oxygen or sulfur, Y is R or R substituted with N(R') 2 , OR', COOR', or SO 3  R', each R' is independently selected from the group consisting of H, alkyl from C 1  to C 15 , and alkaryl and aralkyl from C 7  to C 15 , and n is 0 to 12. 
     
     
       3. A method according to claim 2 wherein said acid hydrazone condensate has the general formula ##STR6## where each R is independently selected from the group consisting of H and alkyl from C 1  to C 6  and Y is a carboxylic acid hydrazide that has an OH or NH 2  substituted aromatic ring. 
     
     
       4. A method according to claim 2 wherein said acid hydrazone condensate has the general formula ##STR7## where each R is independently selected from the group consisting of H and alkyl from C 1  to C 6  and n is 1 to 4. 
     
     
       5. A method according to claim 2 wherein X is sulfur. 
     
     
       6. A method according to claim 2 wherein X is oxygen. 
     
     
       7. A method according to claim 1 wherein said acid hydrazone condensate is a salt. 
     
     
       8. A method according to claim 1 wherein said acid hydrazone condensate is not a salt. 
     
     
       9. A method according to claim 1 wherein said vinyl monomer is vinyl chloride. 
     
     
       10. A method according to claim 1 wherein said scale reducing agent is used with about 1 to about 100 wt % of a surface active agent. 
     
     
       11. A method according to claim 1 wherein said scale reducing agent is used with about 10 to about 500 wt % of an inorganic binder. 
     
     
       12. A method according to claim 11 wherein said inorganic binder is fumed silica. 
     
     
       13. A method according to claim 1 wherein said scale reducing agent is prepared by reacting a carbonyl derivative with a carbonyl compound. 
     
     
       14. A method according to claim 1 wherein said reactor surfaces are coated with a composition containing said scale reducing agent. 
     
     
       15. A method according to claim 1 wherein said scale reducing agent is mixed with said vinyl monomer. 
     
     
       16. A method of inhibiting the formation of scale on reactor surfaces in contact with polymerizing vinyl chloride monomer comprising coating said reactor surfaces with a composition containing a scale reducing agent having the general formula ##STR8## or a salt thereof, where each R is independently selected from the group consisting of H and alkyl from C 1  to C 6 , X is O or S, Y is a carboxylic acid hydrazide that has an OH or NH 2  substituted aromatic ring, and n is 1 to 4. 
     
     
       17. A method according to claim 16 wherein said scale reducing agent has the general formula. ##STR9## 
     
     
       18. A method according to claim 14 wherein scale reducing agent has the general formula 
     
     
       19. A method of inhibiting the formation of scale on reactor surfaces in contact with polymerizing vinyl chloride monomer comprising coating said reactor surfaces with a composition which comprises (A) an acid hydrazone condensate or a salt thereof made by condensing a carbonyl compound having the general formula ##STR10##  with a carbonyl derivative having the general formula ##STR11##  and optionally reacting with a base, where each R is independently selected from the group consisting of H and alkyl from C 1  to C 6 , X is O or S, Y is a carboxylic acid hydrazide that has an OH or NH 2  substituted aromatic ring, and n is 1 to 4; (B) about 1 to about 100 wt % of a surface active agent; and   (C) about 10 to about 500 wt % of an inorganic binder.   
     
     
       20. A method according to claim 19 wherein said inorganic binder is fumed silica.